Materials adapted to exhibit varying visual appearances

ABSTRACT

Sheet material comprising two superimposed differently coloured light-transmitting non-fibrous layers and between the layers and in substantially intimate contact therewith a partially lighttransmitting layer is herein defined, the colors of the lighttransmitting layers being so selected that when either face of the material is viewed by transmitted light from a source of a substantially white light, the color observed is different from that observed when either layer alone is viewed in like manner.

States Pate 1191 Walworth 350/132 Unrt Edwards Dec; Ml", 19741 MATERIALSADAPTED T0 EXHIBIT 2,961,365 11/1960 'sr66 ..L... 161/214 VARYING VISUALAPPEARANCES 1 fib 1xon [75] Inventor: Christopher John Edwards, Marlow,3,065,120 11/1962 Avelar 154/461; England 3,163,554 12/1964 Gess ler161/3 3,264,164 8/1966 Jerothe ct 211.... 161/6 [73] 'A P f dela RueImgmamnal 3,429,733 2/1969 WO1f6la1..... ..117 33.3 Llmlled LOndOILEngland 3,442,755 5/1969 Walters et a1. 162/168 22 Filed. Dec 29 19713,451,877 6/1969 Herschman ..161/3 3,581,417 6/1971 Andrews 40/22 [21] IAppl, No.: 213,706 3,620,888 11/1971 Buzzell 161/1 30 1F Tell it Alicfllio Prio it Data Prim? Amber 1 D :3 F r y 710/70 AssistantExaminer-:William R. Dixon, Jr.

tea n am Attorney, Agent, or Firm-Baldwin, Wight & Brown [52] US. Cl161/3, 40/1.6, 40/5, 1

40/130 B, 40/130 F, 40/135, 40/219, 161/6, [57] ABSTRACT 161/228 0 0 iSheet material comprising two superimposed differ- Km Cl M12 entlycoloured light-transmitting non-fibrous. layers [58] Fieid 232 408 andbetween the layers and in substantially intimate 161/4O9 3 40/l 5contact therewith a partially light-transmitting layer is 1 6 1 6 hereindefined, the colors of the light-transmitting laye'rs being so selectedthat when either face of the ma- 56] References Cited terial is viewedby transmitted light from a source of a substantially white light, thecolor observed is differ- UNITED STATES PATENTS ent from that observedwheneither layer alone is 1,947,516 7 2/1934 Broadman .1 154/40 viewedin like manner. 2,333,641 11/1943 Corwin 2,892,383 6/1959 25 Claims, 41Drawing Figures Ill/11111111177111 MATERIALS ADAPTED TO EXHIBIT VARYINGVISUAL APPEARANCES This invention relates to improvements in sheetmaterials wherein at least one portion thereof exhibits a visualappearance which differs in color in accordance with the angle throughwhich the materials are viewed and/or illuminated.

The said materials have utility in areas such as, for example, theconstruction of playthings, advertising and promotional media, printedarticles generally, teaching, the conveyance of information, theidentification of articles, and as artists or artistic materials per se.

It is desirable that certain printed and other articles, including thoseabove mentioned should incorporate or constitute one or more featuresthat attract the eye and attention of a viewer. By this means,information may be brought to the notice of an observer moreemphatically than is the case with media not exhibiting such a feature.

According to this invention a sheet material comprises at least twosuperimposed differently colored light-transmitting non-fibrous organicpolymer layers and between each adjacent pair of the layers and insubstantially intimate contact therewith is a substantially planarpartially light-transmitting layer as hereinafter defined, the colors ofthe light-transmitting layers being so selected that when either face ofthe material is viewed by transmitted light, from a source ofsubstantially white light, the color observed is different from thatobserved when either layer alone is viewed in like manner.

By a partially light-transmitting layer it is meant a layer which servespartially to reflect and partially to,

transmit light falling upon it; the ratio of the intensity of thetransmitted light to the reflected light being dependent upon the angleof incidence of the light and being a maximum when the angle ofincidence is normal to the partially transmitting layer.

The partially light-transmitting layer maybe any suitable layer havingthe properties defined above and may comprise for example, a fibrillatedplastics layer, a layer of tissue or similarly structured paper, analpha cellulose or similar paper, a layer of particulate matter inspaced distribution, a' layer of transparent material having a surfacefinish adapted to confer a high degree of reflectance-upon the incidencethereupon of nonnormal light rays (for example, a transparent filmprinted on both sides with an ink containing discrete particles of awhite highly refractive pigment such as titanium dioxide) or a web ormesh of textile fabric. The partially transmitting layer may be anadhesive suitable for bonding two light transmitting layers together andyet, when set, possessing the transmission characteristics required ofsuch a layer. No particular limits are to be applied to the thickness ofthe partially light-transmitting layer other than that preferably itshould be as thin as is commensurate with'the exhibition of the abovedefined characteristics.

The organic polymer light-transmitting layers a e preferably selectedfrom the group comprising thermoplastic resins, regeneratedcellulose andcellulose esters and transparent compositions containing the same.However any colored non-fibrous transparent organic polymer materialwill suffice. The layers, which may be preformed or formed during themanufacture of articles according to this invention, are preferably eachof a thickness within the range of 0.0001 inch to 0.1 inch and,preferably still, within the range 0.0005 inch to 0.05 inch. Alight-transmitting layer may be continuous or non-continuous withrespect to an adjacent partially light-transmitting layer; anon-continuous layer may be created by the application to a suitablepartially lighttransmitting layer of organic polymer material byselective coating, printing or like techniques.

Optionally also one or more of the light-transmitting layers maycomprise sheet materials converted to mesh-like configuration by apunching or like operation; depending upon the desired effect to beobtained from and the appearance desired of any given material, thepartially light-transmitting layer or layers may or may not beperforated in accordance with the perforations of the associatedlight-transmitting layers. If more than one of the light-transmittinglayers are perforated or comprise discrete shapes the colored portionsof each layer must be so positioned that, in the sheet material, theyare in at least partial register with at least some of the coloredportions of at least one of the two other light-transmitting layers thusinsuring that at least some of the light travelling normally or nearlynormally through the colored portions of one of the layers also travelsnormally or nearly normally through at least some of the coloredportions of at least one of the other light-transmitting layers.

The external surfaces of the light-transmitting layers may optionally befurther patterned. or decorated by the application thereto oflight-transmitting printed or similarly applied designs.

Materials according to this invention may be adapted to give variegatedeffects overall. For example, a material may comprise two adjacentportions, one in which the superimposed light-transmitting layers are,for example, yellow and blue and the other in which the supe rimposedlayers are, for example, green and violet; thus when viewed undertransmitted light one portion of the material will appear to be greenand the adjacent portion will appear as grey. Such materials may bereadily constructed by producing each element of such a compositeseparately and then arranging portions of each in desired adjacentrelationship. When more than two light-transmitting layers are used theymay each be of a different color or, according to the total numberemployed, two or more of them may be of the same color. However, inorder to obtain the desired colored effect under transmitted light (wheneach is of a different color) three or more such layers must each be ofsuch a configuration that the composite effect of two I layers is notmarred by the presence of any other layer;

thus when using three or more such layers one or more of them ispreferably colored in parts only or perforated to give an equivalenteffect. By the use of a plurality of colored light-transmitting layerswith uncolored portions or spaces between colored portions of each layeraccording to a predetermined overall pattern, viewing by transmittedlight will produce a predetermined pattern, for example, according tothe relative positioning of the colored portions of relevant layers, arecognizable pattern, word or legend in the composite color.

According to the nature and intended use of materials according to thisinvention, the partially lighttransmitting layer may be co-extensivewith its adjacent light-transmitting layers or, provided it is alwayspresent between portions of such layers required to exhibit the desiredeffect under transmitted light, it may be discontinuous in relation toother portions of the lighttransrnitting layers; inv areas where thepartially lighttransmitting layer is not present the combined effect oftwo adjacent light-transmitting layers, under transmitted light, will bedifferent from that obtained if the partially light-transmitting layerwere present. In any event, however, the partially light-transmittinglayer, when present between two differently colored lighttransmittinglayers may be modified to create special effects. For example, within anarea of such a partially light-transmitting layer smaller areascorresponding to the shapes of, for example, letters may be created bystamping out or by selective transparentization of the layer; in such aninstance the letters may appear, when viewed mainly by reflected light,as the color of either of the outermost layers of thelight-transmittinglayers (on the background of the combinative color of the two layers) independence upon the side from which viewing takes place when viewedunder mainly transmitted light, the letters would disappear, tend todisappear, or appear differently within the entire area encompassed bythe partially transmitting layer. Conversely, by opacifying, e.g.,' bythe application of opaque inks, portions of the said area of thelight-transmitting layer in correspondence with, for example, the shapesof letters, the reverse effect will be obtained, that is to say thelettering will be weak under reflected light but will be seen moredistinctly when the material is viewed under mainly transmitted light.

The colored light-transmitting layers and the partially transmittinglayer may be firmly bonded together over substantially the whole oftheir co-extensive surfaces or may be bonded only at the peripheralregions thereof. It is preferred that the materials be bonded togetherover substantially the whole of their co-extensive surfaces in order toguarantee intimate contact and thus to maximize the effectpeculiarthereto. It is, however, important when bonding the layerstogether to insure that-the properties necessary in the partiallytransmit ting layer are maintained'therein and not to employ bondingmeans or tecniques that deleteriously effect the defined properties ofsaid partially transmitting layer. When bonding agents, e.g., adhesives,are used they must be'only'be compatible with and capable of bonding tothe material of the light-transmitting layers but also of such a natureand present in such a quantity that they do not penetrate substantiallyinto the body of the partially light-transmitting layer. To this end,when the partially light-transmitting layer paper, it is preferable'touse a calendered product.

It is preferred that the bonding of the layers is so performed that thebonded layers cannot be readily separated and more preferably it is soperformed that at-- rial may be prepared by adhesively bondingthe'preformed colored light-transmitting layers to the paper or fabricsheet; alternatively the colored layerslmay be prepared by extrusiontechniques known per se for certain of vthe suitable materials and bypositioning and bonding the partially transmitting layer during or immediately after the extrusion in such a manner that the partiallytransmitting layer and the light-transmitting layers becomebonded-togetheras a unitary structure during that period wherein one orboth of the colored light-transmitting layers is in a flowable state.

The materials of the invention may be used alone or in combination withother materials. For example, dis play' cards may be fabricated entirelyof the materials of our invention suitably printed and/or fashioned or adisplay card may be formed, from any suitable base material known forsuch purpose, having affixed into the base material, but selectivelyremovable therefrom in a predetermined and controllable manner, amaterial according to our invention. Furthermore, printed arti cles canbe fabricated in which the materials are incorporated in a non-removablemanner. For example, if the base material for such articles is athermoplastics 'material the materials of our invention can benonremovably-incorp'orated therein by any suitable: means such as, forexample welding, solvent bonding, extrusion or molding. If the basematerial is paper, ournovel materials may be incorporated into thepaper. during the process of manufacturing the paper, preferably bylaying materials according to this invention on a layer of paper pulp inthe paper-making machine and then laying a further layer of paper pulpthereover. Obviously, the thickness of such paper pulp layers must notbe such as to prevent the transmission of light through the incorporatedsheet material. The use of a perforated version of our materialfacilitates the production ofa'coherent body as a result of thepenetration of the paper fibres through the holes in the material sosecurwide range of thicknesses but irrespective of the thicktempts toseparate'the bonded layers results in'the m echanical disruption of oneor more of the layers. Suitably, this preferred. bonding isfp'erformedutilizing,

bonding agents and/or bonding'means such that the strength of the bonds.fonned between lighttransmitting layers and-the partially transmittinglayer or layers exceeds the cohesive strength of the partiallytransmitting layeror/layers and/or'are' at least-as strong ness of thepaper into which the novel materials are to be incorporated it ispreferred'that the materials are so selected that in the'finished papera layerof'paper fibres-at least 0.0005 inch thick overlays each'surface'of the material provided that the thickness and/or opacity of thefiberlayers does not prevent transmis sion of light through the sheetmaterial. However, this restriction is not to be taken as limitingsince, according to the use for the finished product, materialsaccording .tothis invention, when incorporated in paper,

mayv have still thinner overlaying layers of paper fibre or may, inpart, protrude through the surfacesof the paper. Composite articlescomprising the novel materimaterials according to this invention andsuch materials may form a major or a minor part of such composites.

It will be appreciated that, in order for the materials of the inventionto exhibit varying visual appearance, the manner in which they areutilized must be such that light will pass through and onto thematerials and hence they must be so positioned that they may be viewedalternatively by essentially transmitted or essentially reflected light.The function of the partially transmitting layer is such that at lowangles of incidence of viewing and/or illumination the ratio oftransmitted light to reflected light is low and hence the color observedby a viewer is substantially that contained by the colored layer closerto his eye; as the angle of incidence increases towards normal theobserved color changes until, at a normal angle of incidence, the colorobserved is a composite of thetwo differently colored lighttransmittinglayers so long as the degree of illumination onto the surface fartheraway from the observer results in the majority of light falling onto theobservers eye coming from that source of illumination.

In that embodiment of our invention wherein the novel material isincorporated within the body of a paper sheet the best effect isobtained when using a transparent or transparentized region of paperwherein the light entering or leaving the material through the paperlayers is dispersed to a leaser extent than when using known papers.Conveniently, transparentization is efiected subsequent to theproduction of such paper composites by treating the surfaces thereof orthe portions of such surfaces which enclose materials according to thisinvention with a suitable agent, for example a melamine formaldehyderesin, a derivative thereof or other cross-linkable compounds known perse as suitable for the transparentization of paper.

In order that it may be more fully understood certain non-limitingembodiments of the invention are exemplified below with reference to theaccompanying drawings of which FIG. 1 is a diagrammatic exploded view ofthe componentsof the material described in Example I;

FIG. 2 is a plan view showing diagrammatically the disposition within apaper web of the separately produced components of Example-II;

FIG. 3 shows an exploded view of the components of the materialdescribed in Example III; and

FIG. 4 is an exploded view of the components described in Example IV.

EXAMPLE I This example describes a novel sheet material according to ourinvention suitable for incorporation into a paper web during itsmanufacture and also a method for preparing the materials.

As indicated hereinabove, for incorporation into a paper web during itsmanufacture our novel materials are preferably at least 0.001 inchthinner than the finished paper. The material described in this exampleis about 0.003 inch thick and thus is suitable for incorporation intopapers having a finished thickness of at least 0.004 inch.

The novel material according to this example is in perforated web form(although for purposes of simplicity perforations are not shown in; thedrawing) and comprises a central layer 1 of highly calendered alphacellulose paper about 0.002 inch thick having adhered to one sidethereof a blue dyed film 2 formed from polyethylene terephthalate and tothe other side a ye]- low dyed film 3 formed from polyethyleneterephthalate, each layer of polyethylene terephthalate being about0.0005 inch thick.

The novel material was prepared as follows:

i. One surface of each of the films was coated with a two part adhesive4 of the polyester-isocyanate type and the adhesive thoroughly dried bypassage through an oven.

ii. The two films with their adhesive coated surfaces inwards were thenarranged on either side of the paper web and the assembly passed througha hot nip laminator whereby the adhesive was activated and the assemblyconsolidated to a unitary structure in web form.

iii. The web was then passed between cooling rollers and then perforatedbefore being wound upon a take-up spool.

The perforated web was incorporated into paper during a paper-makingprocess by first laying down a layer of paper pulp, positioning theperforated web thereon, and thenapplying to the first down pulp layerand the tape further pulp to build up the paper to the desired thicknessof about 0.004 inch. After drying and finishing the paper in the normalmanner that area of the paper web corresponding to the perforated webmaterial was treated in a known manner by a printing technique with acompositionknown for the transparentization of paper.

The material according to this example was suitable for use per se or incombination with materials other than paper-making pulp.

The novel material prepared as described exhibits, both alone and whenincorporated into the paper web, a visual appearance varying independence upon the angle of the light path by which it was viewed. Whenviewed under transmitted light conditions the material appeared greenwhile in reflected light the material appeared either blue or yellowdependingupon which side of the material was being viewed.

EXAMPLE in Example I was repeated up to and including step (iii) savefor the use of a green dyed film of polyethylene terephthalate in placeof the blue film and a violet dyed film of the same polymer in place ofthe yellow film;

A portion of the material so produced together with a portion of thematerial produced in accordance with Example I, was then incorporated inpaper in accordance with the further description of Example I. The

' portior1 s of Example I and II materials were laid in This materialwas also suitable for use other than in the body of paper pulp.

EXAMPLE in This example relates to a triple'layer materialforincorporation into paper web or sheet, and may be considered to be asymmetrical arrangement based on Example I.

The novel feature of this example is to provide a first color when paperincorporating the material is viewed from either side by reflectedlight, and a second color when viewed from either side by transmittedlight.

Referring to FIG. 3 itwill be seen that the constituents of the materialcomprise a centrally disposed blue dyed film 8 formed from polyethyleneterephthalate of thickness 0.0005 inch and two outwardly disposed yellowdyed films 9 and 10 (also of 0.0005 inch thickness) of a similarmaterial. interposed between the dyed films are disposed alpha cellulosepaper sheets 11 and 12 having a thickness of about 0.002 inch.

The method of preparing the material comprised coating both surfaces ofthe film 8 and one surface each of film 9 and 10, with adhesive 13.Thereafter, the adhesive was dried, the components were than assembledin the manner shown in FIG. 3, and finally were consolidated by heat andpressure.

The material so formed may be perforated if desired and thenincorporated into a paper web in the manner described in Example I.

When theh paper is viewed from either side by reflected light thematerial embedded therein will appear yellow, but when viewed bytransmitted light it will appear green (i.e., the combined effect of allthese films).

The optical effect may be enhanced by transparentization of the paper inthe vicinity of the material.

The material described above was suitable for uses other than in thebody of fibrous substances.

EXAMPLE IV This example relates to material comprising two continuousdifferently colored light-transmitting layers having therebetween adiscontunuous partially transmitting layer which is co-extensive withonly portions of the light-transmitting layers, in order to produce aspecial effect.

The materials are those referred to in Example I. Referring now to FIG.4 layer 14 is yellow and layer 15 is blue. The adhesive layers areindicated at 16. The alpha cellulose layer 17 is shorter in length thaneither of the light-transmitting layers and is so disposed that, at eachend of the composite material the yellow and blue layers, or rather theadhesive coatings thereof are in intimate contact with each other.

The alpha cellulose layer is perforated at 18, said perforations beingrepresentative of portions of letters, say D.L.R.

When material according to this example was viewed mainly by reflectedlight the portions not encompassing the alpha cellulose layer and thoseportions corresponding to the perforations in the alpha cellulose layerappeared green viewed'from either side, and the portions of thelight-transmitting layers having the alpha cellulose layer therebetweenappeared blue when viewed from the blue side and yellow when viewed fromthe yellow side. Thus the green lettering was EXAMPLE V Materialaccording to this invention was produced from three superposed open-workwebs of regenerated cellulose, one being colored violet, one beingcolored green and one being colored yellow and each having a thicknessof 0.001 inch thick and two layers of tissue paper, one between eachadjacent pair of regenerated cellulose webs and co-extensive therewithand each having a thickness of 0.01 inch. The webs were arranged in theabove-mentioned order, that is with the green web centrally placed.

The layers of regenerated cellulose were bonded to the layers of thetissue paper by means of a nitrile rubber based adhesive applied to thewebs prior to their use for the purpose of this invention.

Each web was initially a continuous sheet but each was converted toopen-workform by the stamping-out of predetermined portions in apredetermined pattern. One portion of each element of the violet layerwas arranged to overlie an element of the green layer and an- .otherportion of the violet layer was arranged to overlie an element of theyellow layer.

When the resultant product was viewed by reflected light, one faceappeared of clear violet and diffused green areas and the other faceappeared of clear yellow and diffused green areas. When viewed fromeither side by light transmitted through the material, the appearancewas a pattern of gray, green and brown areas.

Material according to this example was suitable for uses as a materialin its own right although it was also suitable for incorporation withinthe body of a relatively thick paper fibre body.

In alternative embodiments of the invention which may be applied to anyof the above examples or adaptations thereof, an equivalent opticaleffect may be obtained by coating the surfaces of the partiallylighttransmitting layer sheets with light-transmitting color media, (forexample by roller coating techniques). This method serves to provide anextremely compact material, and eliminates the need for adhesives.

Example V relates the use of a partially lighttransmitting layer withcut-out portions but in still further embodiments, which serve toprovide additional unique and artistic effects, and which are alsoapplicable to the above described examples, the partiallylighttransmitting layers may be cut out to provide a pattern, discretelytransparentized or printed 'upon with opaque inks or dyes in apredetermined manner before application of the layers or coatings.

By way of an example applicable to advertising,

' words may first be printed upon the partially lightclearly visible, ona yellow background when viewed transmitting layer in opaque ink andsubsequent to the production of material according to this inventionincorporating such a layer a second printing may be applied to thefrontal surface of a paper sheet enclosing the said material. In use, afirst source of illumination may be directed upon the front of the sheetto display the second printed matter. A further source of illuminationmay be positioned behind the composite sheet, and a suitable switchingmeans may be arranged to render either or both sets of printingselectively visible.

What is claimed is:

1. Sheet material comprising at least two superimposed coloredlight-transmitting non-fibrous organic polymer film-forming layers, eachlayer of a pair of layers being differently colored, and between eachadja- 9 cent pair of said layers and in substantially intimate contacttherewith a single substantially planar layer which is partiallylight-reflecting and partially light-' transmitting with the ratio ofthe intensity of transmitted light to the intensity of reflected lightbeing dependent upon the angle of incidence of the light and being amaximum when the angle of incidence is normal to said layer, the colorsof the light-transmitting layers being 80 selected that when either faceof the composite material is viewed by transmitted light from a sourceof substantially white light the color observed is different from thatobserved when any light-transmitting layer alone is viewed in likemanner.

2. Sheet material as claimed in claim 1 in which each of thelight-transmitting layers has a thickness within the range 0.0001 inchto 0.1 inch.

3. Sheet material as claimed in claim 2 in which the thickness of atleast one light-transmitting layer is within the range 0.0005 inch to0.05 inch.

4. Sheet material as claim in claim 1 in which the overall externalsurfaces thereof comprise continuous light-transmitting layers.

5. Sheet material as claimed in claim 1 in which at least onelight-transmitting layer comprises a layer applied to said partiallylight-reflecting and partially lighttransmitting layer as a coating.

6. Sheet material as claimed in claim l in which at I discontinuouslayer comprises discrete organic poly-' mer areas.

9. Sheet material as claimed in claim 1 in which all of thelight-transmitting layers are discontinous, said layer being so disposedin relation to one another that at least some of the light travellingsubstantially normal to the colored portions of any one layer travelsalso substantially normal to at least some portions of at least oneother layer.

10. Sheet material as claimed in claim 1 including threelight-transmitting layers, the remotely disposed layers being of thesame color and the other layer being of a different color and havingpartially light-reflecting and partially light-transmitting layersbetween each pair of light-transmitting layers.

11. Sheet material as claimed in claim l in which said partiallylight-reflecting and partially light-transmitting layer is formed of afibrous material.

12. Sheet material as claimed in claim l in which said partiallylight-reflecting and partially light-transmitting layer is in the formof a calendlered material of the paper and fabric type.

13. Sheet material as claimed in claim lin which said partiallylight-reflecting and partially light-transmitting layer is in the formof a layer of spaced discrete particles of a light-reflecting material.I l

14. Sheet material as claimed in claim 1 in which said partiallylight-reflecting and partially light-transmitting layer is formed of atransparent material having a surface finish which is highly refiectantof light rays which are not normal thereto.

115. Sheet material as claimed in claim M in. which the partiallylight-reflecting and partially lighttransmitting layer is in the form ofa transparent film printed on both sides with an ink containing discreteparticles of a highly light-refractive pigment.

. 116. Sheet material as claimed in claim l in which there are adhesivemeans bonding-said partially lightreflecting and partiallylight-transmitting layer to said adjacent light-transmitting layers.

layer is coextensive with portions only of said adjacentlight-transmitting layers.

1%. sheet material as claimed in claim l in which portions of saidpartially light-reflecting and partially lighttransmitting layer aretransparent.

19. Sheet material as claimed in claim l in which portions of saidpartially light-reflecting and partially lighttransmitting layer areopaque.

20. A product comprising sheet material as claimed in claim 1incorporated generally centrally within a paper base material with thesheet. material being viewable by light transmitted through saidproduct.

21'. A product as claimed in claim 20 in which said paper base materialincludes a layer of paper fibres having a minimum layer thickness of0.005 inch overlying each surface of the sheet material.

22. A product as claimed in claim 21 in which at least that portion ofeach layer of paper fibres overlying thesheet material are transparent.

23. Sheet material as claimed in claim l wherein said 25. Sheet materialas claimed in claim ll wherein said film-forming materials are celluloseesters.

* i =l l= t

1. SHEET MATERIAL COMPRISING AT LEAST TWO SUPERIMPOSED COLORED LIGHT-TRANSMITTING NON-FIBROUS ORGANIC POLYMER FILMFORMING LAYERS, EACH LAYER OF A PAIR OF LAYERS BEING DIFFERENTLY COLORED, AND BETWEEN EACH ADJACENT PAIR OF SAID LAYERS AND IN SUBSTANTIALLY INTIMATE CONTACT THEREWITH A SINGLE SUBSTANTIALLY PLANAR LAYER WHICH IS PARTIALLY LIGHT-REFLECTING AND PARTIALLY LIGHT-TRANSMITTING WITH THE RATIO OF THE INTENSITY OF TRANSMITTED LIGHT TO THE INTENSITY OF REFLECTED LIGHT BEING DEPENDENT UPON THE ANGLE OF INCIDENCE OF THE LIGHT AND BEING A MAXIMUM WHEN THE ANGLE OF INCIDENCE IS NORMAL TO SAID LAYER, THE COLORS OF THE LIGHT-TRANSMITTING LAYERS BEING SO SELECTED THAT WHEN EITHER FACE OF THE COMPOSITE MATERIAL IS VIEWED BY TRANSMITTED LIGHT FROM A SOURCE OF SUBSTANTIALLY WHITE LIGHT THE COLOR OBSERVED IS DIFFERENT FROM THE OBSERVED WHEN ANY LIGHT-TRANSMITTING LAYER ALONE IS VIEWED IN LIKE MANNER.
 2. Sheet material as claimed in claim 1 in which each of the light-transmitting layers has a thickness within the range 0.0001 inch to 0.1 inch.
 3. Sheet material as claimed in claim 2 in which the thickness of at least one light-transmitting layer is within the range 0.0005 inch to 0.05 inch.
 4. Sheet material as claim in claim 1 in which the overall external surfaces thereof comprise continuous light-transmitting layers.
 5. Sheet material as claimed in claim 1 in which at least one light-transmitting layer comprises a layer applied to said partially light-reflecting and partially light-transmitting layer as a coating.
 6. Sheet material as claimed in claim 1 in which at least one of light-transmitting layers is a discontinuous layers.
 7. Sheet material as claimed in claim 6 in which the discontinuous layer is a perforated layer.
 8. Sheet material as claimed in claim 6 in which the discontinuous layer comprises discrete organic polymer areas.
 9. Sheet material as claimed in claim 1 in which all of the light-transmitting layers are discontinous, said layer being so disposed in relation to one another that at least some of the light travelling substantially normal to the colored portions of any one layer travels also substantially normal to at least some portions of at least one other layer.
 10. Sheet material as claimed in claim 1 including three light-transmitting layers, the remotely disposed layers being of the same color and the other layer being of a different color and having partially light-reflecting and partially light-transmitting layers between each pair of light-transmitting layers.
 11. Sheet material as claimed in claim 1 in which said partially light-reflecting and partially light-transmitting layer is formed of a fibrous material.
 12. Sheet material as claimed in claim 1 in which said partially light-reflecting and partially light-transmitting layer is in the form of a calendered material of the paper and fabric type.
 13. Sheet material as claimed in claim 1 in which said partially light-reflecting and partially light-transmitting layer is in the form of a layer of spaced discrete particles of a light-reflecting material.
 14. Sheet material as claimed in claim 1 in which said partially light-reflecting and partially light-transmitting layer is formed of a transparent material having a surface finish which is highly reflectant of light rays which are not normal thereto.
 15. Sheet material as claimed in claim 14 in which the partially light-reflecting and partially light-transmitting layer is in the form Of a transparent film printed on both sides with an ink containing discrete particles of a highly light-refractive pigment.
 16. Sheet material as claimed in claim 1 in which there are adhesive means bonding said partially light-reflecting and partially light-transmitting layer to said adjacent light-transmitting layers.
 17. Sheet material as claimed in claim 1 in which said partially light-reflecting and partially light-transmitting layer is co-extensive with portions only of said adjacent light-transmitting layers.
 18. sheet material as claimed in claim 1 in which portions of said partially light-reflecting and partially light-transmitting layer are transparent.
 19. Sheet material as claimed in claim 1 in which portions of said partially light-reflecting and partially light-transmitting layer are opaque.
 20. A product comprising sheet material as claimed in claim 1 incorporated generally centrally within a paper base material with the sheet material being viewable by light transmitted through said product.
 21. A product as claimed in claim 20 in which said paper base material includes a layer of paper fibres having a minimum layer thickness of 0.005 inch overlying each surface of the sheet material.
 22. A product as claimed in claim 21 in which at least that portion of each layer of paper fibres overlying the sheet material are transparent.
 23. Sheet material as claimed in claim 1 wherein said film-forming materials are thermoplastic resins.
 24. sheet material as claimed in claim 1 wherein said film-forming materials are regenerated cellulose.
 25. Sheet material as claimed in claim 1 wherein said film-forming materials are cellulose esters. 